After installation of a new radiation therapy system, or after major changes thereto, commissioning is performed by an end user (e.g., medical physicist at the radiotherapy site) prior to use of the system for medical treatment. The goal of the commissioning is to provide a treatment planning system (TPS) with beam data of the radiation therapy system, so that a model of the radiation beam can be constructed and used for subsequent dose calculations. Commissioning is the responsibility of the medical physicist and is performed according to national and international standards.
FIG. 2 shows an exemplary process flow for configuration and use of a radiation therapy system, including installation product acceptance 202, commissioning 206, medical treatment 214, and periodic quality assurance 220. After the radiation therapy system is delivered and installed at a new location, it is subject to acceptance testing 204, which is conducted according to a predetermined procedure (e.g., agreed to by the manufacturer and end user) to ensure that the installed system meets the manufacturer's specifications for the system and end-user-specific contract requirements, as well as to ensure the safety of patients and operators during subsequent use of the radiation therapy system.
The data generated by acceptance testing 204 cannot satisfy the requirements of the commissioning process 206 because beam data for commissioning is dependent on the dose calculation algorithms employed by the TPS. Rather, completion of the installation/acceptance testing 202 ensures that the radiation therapy system meets minimal operational criteria. In contrast, commissioning 206 provides for comprehensive measurements of dosimetric parameters and beam data that are used by the TPS in subsequent treatment planning.
After installation product acceptance 202, commissioning 206 involves the acquisition 208 of beam data at different beam energy levels and system configurations (e.g., multi-leaf collimator settings), for example, according to the protocol set forth in the American Association of Physical Medicine (AAPM), Task Group 106 (TG-106), Report entitled “Accelerator Beam Data Commissioning Equipment and Procedures,” 2008, which is hereby incorporated by reference herein. The resulting commissioning data is input to a beam configuration module 210 that calculates parameters for one or more dose calculation algorithms to be used by the radiation therapy system. The commissioning data and calculated parameters are uploaded to a dose calculation server (DCS) 212 for subsequent use, for example, a central database for one or more radiation therapy systems at a specific site, such as Varian's distributed dose calculation framework (DDCF).
Radiation therapy planning and delivery to patients can only be performed after commissioning of the system has been completed. To provide radiation treatment 214 to any patient, the data and parameters stored by the DCS 212 can be used by TPS 216 to develop all subsequent instructions (e.g., dosage and device configuration for a desired treatment volume) to treat patients at 218 using the radiation therapy system. Periodically as determined at 230 (e.g., on a daily, weekly, monthly, quarterly, and/or an annual basis), the radiation therapy system is subject to quality assurance (QA) 220, for example, in accordance with AAPM, Task Group 142 (TG-142), Report entitled “Quality Assurance of Medical Accelerators,” 2009, which is hereby incorporated by reference herein. At 222, the original commissioning data can be stored as a baseline for later comparison 226 with data 224 reacquired at the time of QA, for example, according to the TG-142 protocol or any other medical physics protocol. The results of the comparison can be provided in a report 228, for example, for use in auditing of some or all of the treatments systems of a particular site or department.
However, this process is not without the possibility of error. Indeed, errors have been known to occur, and it has been suggested by the World Health Organization that as much as 24% of reported radiotherapy incidents with adverse events were due to errors in commissioning (see World Health Organization, “Radiotherapy Risk Profile—Technical Manual). Since the commissioning data is used in dose calculation and treatment planning, an undetected error can affect all of those patients treated before the error is discovered and corrected. Yet the underlying causes of these errors are often not readily determinable during commissioning 206 or later QA 220. For example, systematic errors during the baseline measurements 208 can be repeated during the periodic reacquisition 224, since the same personnel are likely performing both measurements. Thus, even though the original commissioning data 222 is consistent with the reacquired data 224, both sets of data would be erroneous. For example, such a systematic error may be the use of a sensor inappropriate for the radiation field size, which could lead to patients treated with fields of that size receiving higher or lower than desired radiation doses during treatment.
In commissioning 206, users can attempt to identify errors by following system warnings in configuring the beam. However, such warnings are intentionally made lax by the manufacturer of the software used for planning and commissioning to allow for a wide range of different configurations by the end user. Users may also compare their radiation beam data 208 with published beam data or with manufacturer reference data. But such published/reference data tends to be limited to only a few energies or configurations, and thus would not be likely to identify errors at all energies and configurations.
FIG. 3 shows a process flow for configuration and use of a radiation therapy system that was purchased under a contract providing enhanced conformance with factory data and simplified commissioning. The process of FIG. 3 is similar to FIG. 2, except for certain aspects of the installation product acceptance 302, commissioning 306, and periodic quality assurance 320. Only those differences from FIG. 2 are discussed below. In installation product acceptance 302, the testing performed at 304 (e.g., photo-ionization depth) is performed to a tighter tolerance than would normally be required (e.g., in acceptance testing 204 of FIG. 2). After installation product acceptance 302, commissioning 306 relies on the manufacturer's reference beam data 308 instead of separately acquiring beam data 208. Since the acceptance data is not necessarily complete for commissioning and relies on different protocols, the baseline data 322 for subsequent QA 320 may be obtained separately, e.g., by separate acquisition of beam data (similar to 208 of FIG. 2). Nevertheless, the data stored in DCS 212 for treatment planning is the manufacturer reference data rather than acquired data. This may result in substantial time and cost savings in commissioning the radiation treatment system.
Despite the tighter tolerances associated with acceptance testing, the EBC approach is not without issues. For example, EBC controls for photon-ionization depth only, not for other factors that may be relevant to commissioning. Reference beam data from the manufacturer also may not include MLC parameters (e.g., transmission and dosimetric leaf gap (DLG)) or be available for all desired energy levels or field sizes. The user would thus need to measure such parameters and energy levels/field sizes separately for input to beam configuration module 210. Errors during such measurements would thus not be avoided by the EBC process.
Embodiments of the disclosed subject matter may address one or more of the above-noted problems and disadvantages, among other things.